This invention relates to an extravasation detection system and apparatus.
Extravasation is the accidental infusion of an injection fluid such as a contrast medium, a medicinal fluid or the like into tissue surrounding a patient's blood vessel, rather than into the vessel itself. Extravasation can be caused, for example, by fragile vasculature, inappropriate needle placement, or patient movement, causing the infusing cannula to be pulled from the intended vessel or to be pushed through the wall of the vessel. Also, it is possible for the injection pressure to cause the fluid to be ejected from the vessel at the site of cannula penetration.
Certain injected fluids, such as those used for contrast enhancement or in chemotherapy can be toxic to tissue if concentrated and not diluted by blood flow through the vessel. Accordingly, it is important to detect an extravasation occurrence quickly so that injection of the fluid can be halted before a large volume of fluid has been injected into the surrounding tissue.
A number of prior art systems have been proposed for extravasation detection. One such system is disclosed in U.S. Pat. No. 4,647,281 and comprises a microwave antenna which is secured to a patient's skin over an injection site, and a microwave radiometer connected by a coaxial cable to the antenna. The system uses microwave radiation technology to detect abnormal subcutaneous temperature changes in the area of the injection site resulting from extravasation, and to generate a signal responsive to such changes. The signal is used as an alarm to halt injection of the fluid. In one embodiment of the system, two microwave antennas may be used to generate comparative signals between the injection site and an adjacent area of the patient's skin. The patent discloses disposable microwave antennas incorporated in flexible adhesive patches to be attached in conforming relation to the skin, and also indicates that more expensive reusable antennas can be used in the system.